Water harvesting for sustainability in the Indian arid zone of Rajasthan

Increased demographic pressure and societal advancement result in acute water shortage for drinking, agriculture and for industrial purposes. This problem is more severe in the Indian arid zone of Rajasthan which is characterized by low and erratic rainfall, high evaporation rate, and low ground water potential. Some of the most viable water harvesting systems innovated for the sustenance of the local population on a long term basis are the nadi, tanka, and khadin. In many areas, these systems got relegated into relative insignificance with the introduction of a large scale centralized water supply system. However, with an increase in water demand, the traditional systems have been revived and structurally improved for better storage and management of rainwater. The other water harvesting systems which have been found useful and adopted are anicut, gully plugs, water harvesting dams, water spreading, percolation tank, sub-surface barriers, and sand-filled darns. Rainwater harvesting catchment is an integral component of any water harvesting system. The catchment may be an impervious land, roof top or paved surface. Runoff efficiency of different types of roof experimented at Jodhpur ranged from 33 to 85% of monsoon rainfall. In case of highly permeable land surface, a catchment may be treated artificially using a suitable sealant. Among the several waterproofing materials used for catchment treatment, the Janta emulsion was found most effective with 68% runoff efficiency, followed by sodium carbonate with 66% efficiency.